The invention concerns a method for the treatment of substrates, in which the substrates are treated in a treatment fluid and lifted in a reciprocating manner with a lifting device. Furthermore, the invention concerns a device for treating substrates in a treatment fluid with a lifting device.
A device for treating and a drying process, wherein disk-shaped substrates, for instance semiconductor wafers, are lifted with a lifting knife from a substrate carrier above the treatment fluid surface and inserted into guides of a hood, are known from DE 195 46 990 A1 of the applicant of this present patent application. After the treatment fluid has been drained from the treatment container, the dried substrates are lowered into the substrate carrier that has been dried as well and are then removed from the device together with the carrier.
This known device and method have been successfully used in practice. However, they are inefficient regarding the time required for this drying process. Furthermore, for the drying of the substrates the treatment fluid has to be drained, and this is not only time-consuming, but also requires a greater fluid consumption. Because the substrates have to be inserted into the guides of a hood during the lifting from the treatment fluid, a hood of the aforementioned kind is a necessary requirement. However, the insertion of substrates into the guides of the hood is only possible under great difficulties and with the danger of possible substrate breakage, in particular for rectangular and/or square substrates, or is not possible at all.
From EP 0 385 536 A1 a method and a device for drying substrates after treatment in a fluid are known in which the substrates are guided and secured in the guide slots of a fluid container. A lifting element presses the substrates that are held and guided in the guide slots of the fluid container in the upward direction and into an auxiliary cassette whereby the substrates, after complete removal form the treatment fluid, still remain in contact with the lifting element that is wetted with the treatment fluid. Drying of the substrates is thus not entirely ensured especially when the lifting element is at the same time the securing element for the substrates and thus has a relatively large contact area with the substrates.
From U.S. Pat. No. 4,722,752 a device and a method for rinsing and drying semi-conductor wafers are known in which the wafers are inserted into cassettes and lowered into the treatment fluid and are rinsed while positioned in the cassettes. However, these cassettes present great flow resistance for the rinsing process, especially because the wafers that are laterally secured over a large cross-sectional area by grooves or notches within the sidewalls of the cassette can be exposed only to a limited extent to the liquid. The rinsing function is therefore not satisfactory with the known device. Because of the grooves and edges, the cassette, during the upward movement through the treatment liquid surface, will not be completely dried or dried only with great time expenditure because the liquid in the grooves and on the edges can be removed only over a long period of time or not at all because of the capillary action and the minimal possibility of uninhibited flow therefrom. Furthermore, drops are formed at the lowermost points of the substrates as they are removed from the treatment fluid. These last drops represent a great contamination risk and require a large amount of time for drying so that the productivity of the device is reduced. The drying process of this device is thus dissatisfactory with respect to the drying result and the required amount of time for the drying process.
Based on this, the object of the invention is the development of a method and device for the lifting of substrates into and out of a treatment fluid that eliminate the aforementioned drawbacks of conventional devices and, in particular, provides a fast and reliable drying process and lifting procedure with simple means and with a minimum of expenditure, especially for rectangular and/or square substrates.
The object of the invention is inventively solved for a method, in which the substrates are lifted with a first receiving device at least partially out of the treatment fluid and transferred onto a second receiving device that is dry at the time of transfer of the substrates (3) to completely remove the substrates from the treatment fluid (8), by draining the drops forming at the lowest point of the substrates (3) with a drop draining device. During the lifting of substrates, a last drop is forming on the lowest, bottommost part of the substrate that does not drain off or drains only with difficulty. By draining this drop with a drop draining element, this area also is dried fast and reliably. Guides outside of the container, for instance inside a hood, are no longer needed so that guides inside a hood or possibly the hood itself is not required so that handling of rectangular and/or square substrates without the danger of substrate breakage is possible.
In as much as the second receiving device is not already dry, according to an especially advantageous embodiment of the invention, the second receiving device is being dried before it receives the substrates. The second receiving device can advantageously be dried in the same method step as the substrates. The already dried second receiving device advantageously contacts areas of substrates that have already been dried, i.e., that are already above the fluid surface above which the second receiving device is positioned during the transfer of the substrates.
The second receiving device then completely lifts the substrate areas that during the transfer from the first to the second receiving device were still in the treatment fluid, out of the fluid. No substrate area that has already been dried, contacts a receiving area that has yet to be dried. To achieve this, according to this invention, it is not necessary to drain the treatment fluid from the fluid container.
According to an especially advantageous embodiment of the invention, the first and second receiving devices are movable in a vertical direction relative to one another, wherein a reliable, safe transfer of the substrates from the first to the second receiving device is ensured. During the transfer procedure, the substrates continue to be lifted out of the treatment fluid with a generally constant speed without stops or sudden speed changes, thus minimizing the adherence of particles and contaminants at the substrates.
According to another embodiment of the invention, the substrates are loaded into and/or onto the second support of the device for loading the device and are unloaded out of or from the second support for unloading the device. When using the inventive process, no additional guides and no additional substrate carriers are required.
The inventive method is, in particular, advantageous in conjunction with a drying process based on the Marangoni principle, wherein a gas or a gas mixture, for example, isopropyl alcohol, nitrogen or a mixture of these gases is applied to the substrates to be dried, thus accelerating the drying process substantially.
Based on the aforementioned device, wherein a first receiving device lifts the substrates at least partially out of the treatment fluid and a second receiving device takes over the substrates partially lifted by the first receiving device, whereby the second receiving device is dry when receiving the substrates, the object of the invention is inventively further solved by providing a drop draining element that contacts the lowest part of the substrates at least when they have been completely lifted out of the treatment fluid. For rectangular or square substrates, the lowest point of a substrate is a corner of the substrate. The benefits of this improvement are identical to the benefits described above in conjunction with the inventive method. Here, it is also advantageous that the second receiving device is already dry during the transfer of the substrates from the first receiving device, i.e., analog to the drying process for the substrates, has already been dried, when the second receiving device is also lifted out of the treatment fluid. Areas of substrates already dried are only contacted by already dried areas of the second receiving device, so that the substrates do not contact the fluid again.
According to an advantageous embodiment of the invention, the first and second receiving devices are respectively connected to a driven and motion-controlled transport carriage in order to lift and lower the first and second receiving devices in the desired manner.
It is very advantageous in this context when the transport carriages and/or the first and second receiving devices are movable relative to one another. Preferably, the individual travel course and/or the lift speed of the transport carriages as well as their relative motion and/or speed are controllable by at least one control curve. Devices of the aforementioned kind for the motion control of the transport carriages have been described in U.S. Pat. No. 5,902,402 that is incorporated by reference into the present patent application to avoid repetition concerning this embodiment.
It should be noted that the term substrates comprises not only wafers, but all kinds of objects that are being treated in a treatment fluid and subsequently dried. The term substrates thus comprises not only semiconductor wafers, but also, in particular, LCD disks, compact disks, CDs, flat screens, masks, etc.